CN109113029B - Prismatic table pile and prismatic table pile-forest dam - Google Patents
Prismatic table pile and prismatic table pile-forest dam Download PDFInfo
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- CN109113029B CN109113029B CN201811076249.5A CN201811076249A CN109113029B CN 109113029 B CN109113029 B CN 109113029B CN 201811076249 A CN201811076249 A CN 201811076249A CN 109113029 B CN109113029 B CN 109113029B
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B7/00—Barrages or weirs; Layout, construction, methods of, or devices for, making same
- E02B7/02—Fixed barrages
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/10—Deep foundations
- E02D27/12—Pile foundations
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/40—Foundations for dams across valleys or for dam constructions
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Abstract
The invention belongs to the technical field of debris flow prevention and control blocking dams, and discloses a prismatic table pile and a prismatic table pile forest dam. The prismatic table pile comprises a prismatic table pile body and a bottom foundation fixed on the bottom surface of the prismatic table pile, wherein the prismatic table pile body is fixed on the bottom surface of a mud-rock flow river bed through the bottom foundation; the upstream surface of the prismatic table pile body is two buffer surfaces formed after being bent towards the flow direction of the debris flow, and the bending line of the prismatic table pile body is a diversion buffer edge obliquely arranged towards the flow direction of the debris flow. The prismatic table pile forest dam comprises at least one row of prismatic table pile groups, and each row of prismatic table pile groups comprises a plurality of prismatic table piles. The invention reduces the impact force, the shearing risk, the groove bottom erosion, the damage of the debris flow to the structure and the possibility of foundation failure.
Description
Technical Field
The invention belongs to the technical field of debris flow prevention and control blocking dams, and particularly relates to a prismatic table pile and a prismatic table pile forest dam.
Background
The mud-rock flow prevention and control work starts from the 50 th century in China, and a mud-rock flow basin comprehensive treatment system mainly comprising stability, blocking and discharging is formed. At present, gravity type solid barrages are commonly used in debris flow prevention and control projects in China. In recent years, permeable barrages are also becoming widely used in debris flow control projects. Although the debris flow blocking dam is widely applied to debris flow prevention in China, the national standard of debris flow prevention engineering design is not established in China so far, and only geological mineral industry standard (DZ/T0239-2004) is issued.
The damage form of the debris flow is mainly characterized by silting and impact damage, and particularly the impact damage is most remarkable. The dynamic pressure of the debris flow slurry and the impact force of the entrained rock are direct factors of the failure of the debris flow blocking structure, wherein the impact force of the entrained rock is often the most dominant load of the blocking structure. Debris flow occurring in southwest areas of China generally carries a large amount of stones, and if the stones cannot be effectively intercepted timely, huge impact is generated on various blocking structures or other buildings at the middle and downstream, so that the debris flow is seriously damaged. The adoption of a single debris flow prevention engineering measure is high in cost and huge in investment, or the single debris flow prevention engineering measure is difficult to bear the impact load from the debris flow disaster body. At present, the pile forest structure has the advantages of high rigidity, strong impact resistance, good blocking effect, good durability and the like, and has gradually developed into a relatively common debris flow block blocking structure. The cross section of the pile forest structure is usually round or rectangular, but when facing to a high-speed flowing debris flow disaster body, the pile forest structure of the type always bears huge impact load, so that the cross section of the pile forest structure is generally larger, and the pile forest structure is heavy and wastes more.
In order to effectively separate water from stone and block stone for water delivery, the structures of the traditional pile-forest dams are mainly of two types. The first type is a traditional pile forest (shown in figure 7 in the attached drawings of the specification), which is independently arranged, can be arranged in a row on a plane, is arranged in a multi-inverted V shape (quincuncial shape), and is provided with ground beams between piles, wherein the ground beams are made of reinforced concrete and steel pipe concrete, and the cross section of the ground beams is round or rectangular. From the aspect of prevention and control action mechanism, the pile forest dissipates energy of partial small stones by intercepting large stones in the debris flow, reduces the average flow velocity of the debris flow, provides more favorable conditions for downstream engineering treatment, mainly bears the impact load of the stones in the debris flow, and also bears the pressure of the debris flow. The other type is a traditional grid pile (shown in figure 8 in the attached drawings), and the biggest difference from the first type is that a plurality of transverse tie beams are arranged, the pile piles are combined into a whole, the rigidity of the structure is increased, and a grid dam is formed. Thus, strictly speaking, the first type is a pile dam and the second type is a grid dam. From the aspect of prevention and control action mechanism, the second class more effectively improves the capability of intercepting the stone block, improves the water-stone separation efficiency, and naturally bears larger load, but the probability of damage is reduced due to the increase of structural rigidity and integrity, thus being an improvement of the first class.
Through analysis of prevention and control action mechanisms, structural defects of the traditional pile-forest dam are not difficult to find, single piles of the traditional pile-forest dam are easy to shear and damage because of bearing huge block stone impact load, and meanwhile, the front faces of the single piles are rectangular and bear huge fluid pressure, so that the design of the single pile structure needs to consider powerful strength and rigidity guarantee, and the single pile-forest dam has thick structure, large masonry quantity and more waste. The traditional grid pile forest dam partially compensates for the defect and improves the structural rigidity, but because of the impact resistance, the structure still needs to be provided with a larger masonry, but because the front surface is subjected to impact and fluid pressure, the shearing resistance of the structure is not obviously improved, and the engineering waste is still larger.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a prismatic table pile and a prismatic table pile forest dam.
The technical scheme adopted by the invention is as follows:
the prismatic table pile comprises a prismatic table pile body and a bottom foundation fixed on the bottom surface of the prismatic table pile, wherein the prismatic table pile body is fixed on the bottom surface of a mud-rock flow river bed through the bottom foundation; the upstream surface of the prismatic table pile body is two buffer surfaces formed after being bent towards the flow direction of the debris flow, and the bending line of the prismatic table pile body is a diversion buffer edge obliquely arranged towards the flow direction of the debris flow.
It is further preferable that the prismatic table pile body has a triangular table structure, and the projection of the center of gravity of the upper bottom surface of the prismatic table pile body on the lower bottom surface coincides with the center of gravity of the lower bottom surface; two of the three side surfaces of the prismatic table pile body are the buffer surfaces, and the other side surface is a slope surface.
Still more preferably, the upper bottom surface of the prismatic pile body is an isosceles triangle, one waist of the isosceles triangle is one side of one buffer surface, and the other waist of the isosceles triangle is one side of the other buffer surface.
Still more preferably, the upper bottom surface of the prismatic table pile body is a regular triangle.
Still further preferably, the bottom foundation includes a shallow foundation fixed to the lower end of the prismatic pile body and a deep foundation fixed to the lower end of the shallow foundation, and the area of the cross section of the deep foundation is smaller than the area of the lower end face of the shallow foundation.
Still more preferably, the prismatic table pile body and the shallow foundation are both made of fiber concrete, and the deep foundation is made of ordinary concrete.
The prismatic table type pile forest dam comprises at least one row of prismatic table pile groups, wherein each row of prismatic table pile groups comprises a plurality of prismatic table piles.
It is further preferable that the prismatic table pile group is provided with at least two rows, and prismatic table pile bodies in the adjacent two rows of prismatic table pile groups are arranged in a staggered manner, and any one prismatic table pile body is positioned on a middle vertical line of two prismatic table pile bodies in the adjacent another row of prismatic table pile groups.
Still more preferably, the side length of the upper bottom surface of the prismatic table pile body is at least 1m, and the minimum spacing s between two adjacent prismatic table pile bodies in each row of prismatic table pile groups is 0.6-0.8m; the spacing between two adjacent rows of prismatic table pile groups is at least 3m.
It is further preferred that the lower end of at least one of the bottom foundations is fixed with a tongue and/or anchor structure.
The beneficial effects of the invention are as follows:
1) The part (namely the prismatic table pile body) which is subjected to impact load above the ground is adjusted to be two buffer surfaces formed after the upstream surface is bent towards the flow direction of the debris flow, so that the stress state when the front collision is subjected to the impact of the debris is improved, the front collision is adjusted to be an angle collision, and the collision impact force is reduced;
2) According to the prismatic table type pile forest dam, the pressure of fluid is regulated to be split from the front stress, and the bending is regulated to be lateral stress of a symmetrical structure, so that the risk of shearing of the structure is reduced;
3) When the debris flow acts on the prismatic table type pile forest dam, the two buffer faces exert upward thrust against the debris flow, so that the movement direction of the debris flow is adjusted, the groove bottom erosion effect is reduced, and the structural safety of the invention is favorably protected;
4) The quasi-laminar state of the debris flow is adjusted to the turbulent state in a planned way through the interception of the prismatic pile forest dam, the average flow velocity is reduced by utilizing the viscous action of the debris flow, so that the impact energy is reduced, and the damage capability to the structure is reduced;
5) A shallow foundation with a certain depth is buried below the terrace, so that most of thrust of horizontal load applied by the debris flow is borne, and meanwhile, the bearing capacity of the foundation is improved by utilizing the deep foundation, and foundation failure caused by vertical load of the debris flow is avoided;
6) Assuming that the triangular platform structure is damaged, according to the principle of triangle (upper bottom surface and lower bottom surface) and tetrahedron (three side surfaces) stabilization, after any one of the surfaces is contacted with the ground, the stability is maintained to the greatest extent (sliding friction rather than rolling friction is generated between the triangular platform structure and the debris flow), and a blocking effect can still be formed on the debris flow in theory;
7) In space, the whole structure is not required to be connected by adopting a transverse tie beam, the functions similar to the flow guiding and blocking of a gap dam are formed between the dams, and at least two rows of prismatic table pile groups are arranged, so that higher efficiency can be exerted;
8) The mud-rock flow collides with the buffer surface, and a diamond space exists between the mud-rock flow and the rear row of the prismatic table bodies after passing through the slit between the two prismatic table bodies, so that vortex flow is formed, the flow speed is reduced, the flow direction is changed, and the blocking and the retaining of the massive rock are facilitated.
Drawings
FIG. 1 is a schematic view of the structure of the present invention with two rows of land pile sets;
FIG. 2 is a view A-A of FIG. 1;
FIG. 3 is a schematic view of the structure of the present invention in a third embodiment;
fig. 4 is a schematic diagram of a motion curve y=f (x) when β changes;
FIG. 5 is a schematic view of a structure of a square-frustum-shaped pile-forest dam according to an embodiment;
FIG. 6 is a schematic view of a fifth embodiment of a prismatic table type pile-forest dam;
FIG. 7 is a schematic view of a conventional pile forest;
fig. 8 is a schematic structural view of a conventional grid pile forest.
In the figure: 1-a prismatic table pile body; 11-shallow foundation; 121-a slope surface; 122-buffer surface; 123-split buffer ribs; 2-deep foundation; 3-tenons; 4-anchorage structure.
Detailed Description
The invention is further illustrated by the following description of specific embodiments in conjunction with the accompanying drawings.
Embodiment one:
as shown in fig. 1 to 4, the present embodiment provides a prismatic pile, which comprises a prismatic pile body 1 and a bottom foundation fixed on the bottom surface of the prismatic pile, wherein the prismatic pile body 1 is fixed on the bottom surface of a mud-rock flow river bed through the bottom foundation; the upstream surface of the prismatic table pile body 1 is two buffer surfaces formed after being bent towards the flow direction of the debris flow, and the bending line is a diversion buffer rib 123 obliquely arranged towards the flow direction of the debris flow. The height of the prismatic pile body 1 is determined according to the height of the debris flow tap.
Preferably, the prismatic pile body 1 has a triangular platform structure, and the projection of the center of gravity of the upper bottom surface of the prismatic pile body 1 on the lower bottom surface coincides with the center of gravity of the lower bottom surface, so that the prismatic pile body 1 has the best stability; two of the three side surfaces of the prismatic table pile body 1 are the buffer surfaces 122, and the other side surface is the back surface 121, namely the back surface 121 is positioned in the back surface direction of the debris flow.
Preferably, the upper bottom surface of the prismatic pile body 1 is an isosceles triangle, one waist of the isosceles triangle is one side of one buffer surface, and the other waist of the isosceles triangle is one side of the other buffer surface.
The gradient of the shunt buffering rib is smaller than that of the back slope surface 121, namely, a surface parallel to the lower bottom edge of the back slope surface 121 in the plane of the shunt buffering rib is a shunt surface, and the gradient of the shunt surface is smaller than that of the back slope surface 121. The gradient of the split flow surface is preferably 1:0.6, the gradient of the back slope surface 121 is preferably 1:0.3, the most material is saved on the basis of ensuring stability, and the gradient of the split flow buffering edge can be 1:0.5 correspondingly, and the gradient of the back slope surface 121 is 1:0.1.
Preferably, the bottom foundation comprises a shallow foundation fixed at the lower end of the prismatic table pile body 1 and a deep foundation 2 fixed at the lower end of the shallow foundation 11, the depth is not less than the scouring depth of a field, the area of the cross section of the deep foundation is far less than the area of the lower end face of the shallow foundation, the shallow foundation can be in a triangular prism or triangular prism shape corresponding to the prismatic table pile body 1, the shallow foundation 11 and the prismatic table pile body 1 are of a regular integrated design, waste is avoided, the overall stability is also improved, the deep foundation can be cylindrical, square column and the like, the deep foundation is preferably cylindrical, the overall structure scale can be reduced, the horizontal load applied by partial debris flow is born, the structural damage risk caused by failure of the shallow foundation of the triangular prism structure is made up, the overall structure stress is transmitted to the deep part, and the overall stability of the structure is improved.
Preferably, the prismatic table pile body 1 and the shallow foundation 11 are both made of fiber concrete, and the deep foundation 2 is made of common concrete; reinforcing steel bars are paved in the prismatic table pile body, the shallow foundation and the deep foundation, and the reinforcing steel bars can strengthen the overall structural strength. In terms of materials, the prismatic table pile body 1 subjected to impact and the shallow foundation 11 adopt fiber concrete, and the fiber concrete is made of viscoelastic plastic, so that the structural stress state is improved, and the impact resistance of the prismatic table pile body 1 is improved: the brittle failure of the concrete is adjusted to the ductile failure of the fiber concrete, so that the service life of the prismatic pile-forest dam structure is prolonged, the concrete fiber concrete can be steel fiber concrete or basalt fiber concrete and the like, the cost of the common concrete is relatively low, and the common concrete is fixed in depth, so that the cost can be saved while the concrete is reinforced.
Embodiment two:
this embodiment is a further improvement made on the basis of the first embodiment, and the specific differences between this embodiment and the first embodiment are:
preferably, the upper bottom surface of the prismatic table pile body 1 is a regular triangle, that is, the prismatic table pile body 1 is a regular triangular table, at this time, the upper bottom surface of the prismatic table pile body 1 is an equilateral triangle, and the upper bottom surface of the prismatic table pile body 1 may also be an isosceles triangle, one waist of the isosceles triangle is one side of one buffer surface, and the other waist of the isosceles triangle is one side of the other buffer surface.
Embodiment III:
the present embodiment is a further improvement made on the basis of the first embodiment or the second embodiment, and the specific differences between the present embodiment and the first embodiment or the second embodiment are:
the prismatic table type pile forest dam comprises at least one row of prismatic table pile groups, wherein each row of prismatic table pile groups comprises a plurality of prismatic table piles.
Embodiment four:
the embodiment is a further improvement on the basis of the third embodiment, and the specific differences between the embodiment and the third embodiment are:
preferably, the prismatic table pile groups are at least provided with two rows, and the prismatic table pile bodies 1 in the adjacent two rows of prismatic table pile groups are arranged in a staggered manner. For example, when the invention needs to be provided with three rows of prismatic table pile groups, two corresponding prismatic table pile bodies 1 can be arranged for the first row, three corresponding prismatic table pile bodies 1 are arranged for the second row, two corresponding prismatic table pile bodies 1 are arranged for the third row, the two prismatic table pile bodies 1 are combined into a quincuncial intersecting arrangement form, and the quincuncial refers to one form of staggered arrangement in plane arrangement, wherein the concrete arrangement shape of the prismatic table pile dam can be a chessboard arrangement as shown in fig. 5. The number of the prismatic table pile bodies 1 in each row is calculated and determined according to L/(d+s) (L river channel width, d is the width of the bottom of the prismatic table, and s is the slit width); the terrace-edge dams are generally provided with 3-4 rows of terrace-edge pile groups.
Preferably, any one of the prismatic table pile bodies 1 is located on the middle vertical line of two prismatic table pile bodies 1 in another row of prismatic table pile groups adjacent to the prismatic table pile body.
Preferably, the side length of the upper bottom surface of the prismatic table pile body 1 is at least 1m, the minimum spacing s between two adjacent prismatic table pile bodies 1 in each row of prismatic table pile groups is determined according to the particle size of the large stone wrapped by the debris flow, and the limiting particle size is D30 (the equivalent diameter of 30% of the mass percentage of the broken stone wrapped by the debris flow) and is generally 0.6-0.8m, as shown in fig. 1; the row spacing clear distance of the prismatic table pile body 1 is set according to the maximum particle size of the mud-rock flow wrapped and clamped stone, and the distance between two adjacent rows of prismatic table pile groups is at least 3m.
Fifth embodiment:
the embodiment is a further improvement on the basis of the fourth embodiment, and the specific differences between the embodiment and the fourth embodiment are:
as shown in fig. 6, the concrete arrangement shape of the prismatic table pile forest dam can also be in a wedge-shaped arrangement (the number of prismatic table pile bodies in each row of prismatic table pile groups from front to back is changed in the sequential increasing or decreasing manner), so that the structure has stronger anti-scouring capability.
Example six:
as shown in fig. 3, preferably, the lower end of at least one bottom foundation is fixed with a tenon and/or an anchor structure, that is, the lower end of the bottom foundation may be fixed with only the tenon, or only the anchor structure, or the tenon and the anchor structure are fixed together, where the upper bottom surface of the prismatic pile body in the embodiment is an isosceles triangle except for the one where the isosceles triangle is arranged, when the shear strength of the foundation is insufficient, the tenon is additionally arranged at the bottom of the shallow foundation according to practical situations, and the size is determined according to calculation, where the anti-overturning stability of the structure is insufficient, the anchor structure needs to be arranged on the shallow foundation. The tenons 3 can improve the shearing resistance of the prismatic table type pile forest dam structure, and the setting number and setting positions of the tenons 3 can be fixed according to actual conditions, wherein the tenons 3 can be fixed at the lower ends of part of the shallow foundations 11, and the tenons 3 can be fixed at the lower ends of all the shallow foundations 11; the anchor structure 4 saves masonry while improving the pressure bearing capacity, the anchor structure 4 adopts the existing anchoring, and the same set number and set positions of the anchor structure 4 can be fixed according to actual conditions, and the anchor structure 4 can be fixed at the lower end of a part of shallow foundation 11 or the anchor structure 4 can be fixed at the lower end of all shallow foundations 11.
The beneficial effects of the invention are as follows:
1) The part (namely the prismatic table pile body 1) which is subjected to impact load above the ground is adjusted to be two buffer surfaces formed after the upstream surface is bent towards the flow direction of the debris flow, so that the stress state when the front collision is subjected to the impact of the debris is improved, the front collision is adjusted to be an angle collision, and the collision impact force is reduced;
2) According to the prismatic table type pile forest dam, the pressure of fluid is regulated to be split from the front stress, and the bending is regulated to be lateral stress of a symmetrical structure, so that the risk of shearing of the structure is reduced;
3) When the debris flow acts on the prismatic table type pile forest dam, the two buffer faces exert upward thrust against the debris flow, so that the movement direction of the debris flow is adjusted, the groove bottom erosion effect is reduced, and the structural safety of the invention is favorably protected;
4) The quasi-laminar state of the debris flow is adjusted to the turbulent state in a planned way through the interception of the prismatic pile forest dam, the average flow velocity is reduced by utilizing the viscous action of the debris flow, so that the impact energy is reduced, and the damage capability to the structure is reduced;
5) A shallow foundation with a certain depth is buried below the terrace, so that most of thrust of horizontal load applied by the debris flow is borne, and meanwhile, the bearing capacity of the foundation is improved by utilizing the deep foundation, and foundation failure caused by vertical load of the debris flow is avoided;
6) Assuming that the triangular platform structure is damaged, according to the principle of triangle (upper bottom surface and lower bottom surface) and tetrahedron (three side surfaces) stabilization, after any one of the surfaces is contacted with the ground, the stability is maintained to the greatest extent (sliding friction rather than rolling friction is generated between the triangular platform structure and the debris flow), and a blocking effect can still be formed on the debris flow in theory;
7) In space, the whole structure is not required to be connected by adopting a transverse tie beam, the functions similar to the flow guiding and blocking of a gap dam are formed between the dams, and at least two rows of prismatic table pile groups are arranged, so that higher efficiency can be exerted;
8) The mud-rock flow collides with the buffer surface, and a diamond space exists between the mud-rock flow and the rear row of the prismatic table bodies after passing through the slit between the two prismatic table bodies, so that vortex flow is formed, the flow speed is reduced, the flow direction is changed, and the blocking and the retaining of the massive rock are facilitated.
Comparative advantages of the present invention:
whether the prismatic pile-forest dam has popularization and utilization values or not needs comprehensive consideration from the aspects of structure, stress, investment (manufacturing cost) and the like. Through qualitative comparison (as shown in table 1), compared with the traditional structure, the invention has better construction feasibility, more reasonable structure stress state and more reliable structure safety.
TABLE 1 characteristics and quality analysis of traditional pile and forest dam structure and novel pile and forest
The same orifice comparison for investment estimation will also be made below. Taking a dam height of 6m and a channel width of 20m as an example, assuming that the flow speed of the debris flow is 5m/s, the diameter of large solitary stone in the debris flow is required to be intercepted to be 3m, and the structural form, engineering quantity and investment estimation of various pile-forest dams are preliminarily framed (as shown in table 2).
TABLE 2 investment estimation evaluation analysis of traditional pile and forest dam structure and novel pile and forest
The price of the reinforced concrete in Table 2 was 5000 yuan/m 3 Estimating the price of the steel fiber concrete according to 8000 yuan/m 3 And (5) estimating. The cost of a single pile of a traditional pile forest is estimated to be about 42 ten thousand yuan, the cost of a traditional grid pile Lin Shanzhuang is estimated to be about 37 ten thousand yuan, and the cost of the invention is estimated to be about 31 ten thousand yuan. The novel prismatic pile-forest dam has obvious advantages from the total price and the unit price, and from the evaluation, analysis and estimation of the manufacturing cost. Analyzing the reason, from the viewpoint of the construction cost of the single pile: the traditional pile forest needs stronger rigidity and strength, the single pile has large sectional area and the masonry volume is 84 times; the traditional grid pile forest increases the structural integrity of the system due to tie beam connection, improves the structural rigidity, reduces the cross section area of the single pile, slightly reduces the masonry amount, and leads the single pile to be 74.4 square after tie beam spreading; the invention reduces the sectional area of the foundation pile foundation only by the shearing resistance requirement due to the large rigidity and strength of the prismatic table, the volume of the single pile masonry is 46.8 square, and the volume of the prismatic table masonry is 26.2 square (36 square of the common pile masonry with the same length). From the total price point of view: the traditional pile forest and the traditional grid pile forest have large bottom area, the net spacing is reduced, the pile center spacing is increased, and the total number of piles is reduced.
The structural stress calculation of the invention:
when the large block level in the debris flow is V 0 The velocity moves rightwards (relative direction, as shown in fig. 2, i.e. the flow direction of the debris flow, the following is similar), hits the right side pile-forest dam barrier (concrete structure, i.e. the prismatic pile Lin Ba of the present invention), when the inclination angle beta of the barrier changes, the reflection velocity V after collision R And the motion curve y=f (x) after collision will be approximately as shown in fig. 4 (a), (b), (c) and (d), being the motion curve y=f (x) when β=90 °, β > 60 ° ±, β=60 ° ±and β < 60 ° ±respectively.
Energy loss exists in the collision process, and the reflection speed V R The magnitude of (2) may be expressed by a crash recovery coefficient. Let the initial velocity be V 0 Tangential velocity of V 0t Normal velocity is V 0n The method comprises the steps of carrying out a first treatment on the surface of the The reflection speed is V R Tangential reflection speed of V Rt The normal reflection speed is V Rn The method comprises the steps of carrying out a first treatment on the surface of the The tangential recovery coefficient of collision is e t Normal recovery coefficient e n They have the following relationship:
according to engineering experience, the initial speed V 0 Not so much, when the obstacle inclination angle β=60° ±the reflection speed direction is substantially vertically upward as shown in (c) of fig. 4, and when the tangential direction and the normal direction recovery coefficient have a relationship of formula 4-1, the two coefficients are theoretically equal when β=45°.
For a single block, when the obstacle is a plane, its impact force can be calculated according to newton's law using equation 4-2:
mΔv=fΔt, formula 4-2;
Δt is collision time, which can be 0.07 s-0.08 s, and high value when the speed is low. The result is an average impact force that is less than the peak impact force and the structure is unsafe. And can consult the actual measurement data of the impact force of the falling rocks and the maximum impact force calculation empirical formula 4-3 deduced by Hertz elastic collision theory of the Japanese road public group to check:
in the formula 4-3, P is the maximum impact force (kN) of the falling rocks, m is the mass (t) of the impact objects, lambda is Law Mei Jishu, the recommended value is 1000 kN.m-2, and H is the free-falling height (m) expressing the impact speed of the falling rocks. To adapt to the structural model, H is converted into the formula 4-4:
when the inclination angle of the obstacle is smaller than 45 degrees, the lateral recovery coefficient is theoretically smaller than the normal recovery coefficient, and the tangential recovery coefficient is recommended to be 0.1-0.5, and the normal recovery coefficient is recommended to be 0.3-0.7. And (5) calculating shearing resistance:
when the obstacle is a plane and is impacted by a single block, the calculated value P of the maximum impact force can be adopted as the impact force, and the shearing force in the horizontal direction is the corresponding component P of the calculated value Horizontal level Closely related to the value of the coefficient of restitution (formulas 4-5):
let the intersection angle of the reflection speed and the obstacle slope be alpha, the coefficient of restitution also has the following relationship:
in order to sufficiently estimate the degree of failure of the impact force, tangential correction may not generally be performed.
Because the debris flow is composed of a block and a viscous or dilute fluid, the fluid pressure needs to be considered, and the debris flow can be estimated according to the principle. The total pressure per section is then equal to the sum of the pressures on the upstream face. Considering the sides of the prismatic table structureTo the impact surface structure, the total fluid pressure ΣP can be calculated in a two-step manner 0 : (1) the projected area pressure summation Sigma P of the upstream surface is larger in estimated result; (2) according to the inclined plane collision principle, calculating and correcting by utilizing a geometric principle and 4-6:
the calculation thereafter is the force calculation of the structure. For example, the shear strength of any section of the prismatic table is calculated, the sectional area of the prismatic table is S, and the shear stress Q is:
(here Σp is the total pressure summation of the cantilever segments);
it should be noted that, the shearing resistance rechecking of the pile foundation under the terrace with the edge needs to consider the effect of the terrace with the edge dead weight G and the mud-rock flow impact force on the additional compressive stress F of the foundation, which is also the reason that the terrace with the edge needs a certain foundation burial depth.
The basic shear stress is of the formula 4-7:
wherein:for maximum static friction coefficient, equivalent internal friction angle +.>Is the cross-sectional area.
Anti-capsizing calculation:
the anti-overturning mechanism of the structure is very complex, namely overturning after pile pulling, overturning after shearing or yielding after basic plastic yielding, and is difficult to simulate one by one. Here, only the calculation approximation formula derivation of the capsizing calculation after the pulling-up is performed, and the burying depth H of the pile foundation is calculated.
In the formulas 4-8, K is a safety coefficient, L is a vertical distance from the center of the pile to the north edge of the terrace, and h is the terrace height.
The horizontal thrust borne by the prismatic table is used as concentrated load to be simplified, and the action of uniformly distributed load of the stress points with reference to the uniform section is simplified to be 1/3 of the height. In fact, the gradient (acceleration) of increasing the acting force of the prismatic table is larger than the uniform load with the uniform cross section along with the decrease of the height, so that the actual safety margin is higher than the uniform load with the uniform cross section.
The invention is further described with the points, and the invention is characterized in that the prismatic stand type pile forest dam is not suitable for single use when being specifically applied, so that firstly, the aim of prevention and control is definitely established, the reasonable treatment requirement is formulated, and if the water delivery requirement for stone blocking is urgent, the prismatic stand type pile forest dam is a better choice. Meanwhile, the treatment capability of the structure is correctly evaluated, and the use, single row or multiple rows, single channel or multiple channels, and combined application schemes combined with other devices, such as grid mesh, comb dams, check dam and the like, of the prismatic pile-forest dam are determined, so that the prismatic pile-forest dam can take the advantages into consideration and exert the greatest benefit. Finally, after the scheme setting is completed, the linkage operation should be simulated for effect checking.
The invention is not limited to the alternative embodiments described above, but any person may derive other various forms of products in the light of the present invention. The above detailed description should not be construed as limiting the scope of the invention, which is defined in the claims and the description may be used to interpret the claims.
Claims (8)
1. The prismatic table pile is characterized in that: the concrete pile comprises a prismatic table pile body and a bottom foundation fixed on the bottom surface of the prismatic table pile, wherein the prismatic table pile body is fixed on the bottom surface of a mud-rock flow river bed through the bottom foundation; the upstream surface of the prismatic table pile body is two buffer surfaces formed after being bent towards the flowing direction of the debris flow, and the bent line is a diversion buffer edge obliquely arranged towards the flowing direction of the debris flow; the prismatic table pile body is of a prismatic table structure, and the projection of the gravity center of the upper bottom surface of the prismatic table pile body on the lower bottom surface is overlapped with the gravity center of the lower bottom surface; two side surfaces of the three side surfaces of the prismatic table pile body are the buffer surfaces, and the other side surface is a slope surface; the bottom foundation comprises a shallow foundation fixed at the lower end of the prismatic table pile body and a deep foundation fixed at the lower end of the shallow foundation, and the area of the cross section of the deep foundation is smaller than that of the lower end face of the shallow foundation; the deep foundation is cylindrical or square cylindrical.
2. A prismatic table pile according to claim 1, characterized in that: the upper bottom surface of the prismatic table pile body is an isosceles triangle, one waist of the isosceles triangle is one side of one buffer surface, and the other waist of the isosceles triangle is one side of the other buffer surface.
3. A prismatic table pile according to claim 2, characterized in that: the upper bottom surface of the prismatic table pile body is in a regular triangle shape.
4. A prismatic table pile according to claim 1, characterized in that: the prismatic table pile body and the shallow foundation are both made of fiber concrete, and the deep foundation is made of common concrete; reinforcing steel bars are paved in the prismatic table pile body, the shallow foundation and the deep foundation.
5. The utility model provides a prismatic table formula stake forest dam which characterized in that: comprising at least one row of prismatic pile groups, each row comprising a plurality of prismatic piles according to any of claims 1-4.
6. A prismatic stand pile dam according to claim 5, wherein: the prismatic table pile groups are at least provided with two rows, prismatic table pile bodies in the adjacent two rows of prismatic table pile groups are arranged in a staggered mode, and any one prismatic table pile body is positioned on a middling line of two prismatic table pile bodies in the adjacent other row of prismatic table pile groups.
7. A prismatic stand pile dam according to claim 6, wherein: the side length of the upper bottom surface of the prismatic table pile body is at least 1m, and the minimum spacing s between two adjacent prismatic table pile bodies in each row of prismatic table pile groups is 0.6-0.8m; the spacing between two adjacent rows of prismatic table pile groups is at least 3m.
8. A prismatic stand pile dam according to claim 5, wherein: the lower end of at least one bottom foundation is fixed with a tenon and/or an anchorage structure.
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| CN111238767B (en) * | 2020-01-21 | 2021-10-26 | 中国地质环境监测院 | Simulation test platform for impact-resistant blocking structure of high-position landslide fragment flow |
| CN111809537B (en) * | 2020-07-22 | 2021-12-07 | 中国科学院、水利部成都山地灾害与环境研究所 | Design method of collapse landslide blocking energy dissipation pile array |
| CN112211164B (en) * | 2020-10-20 | 2021-07-02 | 同济大学 | Debris flow pile group type blocking structure and method |
| CN112813921B (en) * | 2021-01-06 | 2022-06-07 | 西南科技大学 | Mud-rock flow water-stone separation and storage system |
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| JP2001207431A (en) * | 2000-01-21 | 2001-08-03 | Shigeru Ito | Debris flow disaster protection dam |
| CN104878769A (en) * | 2015-06-19 | 2015-09-02 | 中国电建集团成都勘测设计研究院有限公司 | Debris flow protecting system |
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| CN204163090U (en) * | 2014-10-21 | 2015-02-18 | 中国科学院、水利部成都山地灾害与环境研究所 | A kind of for the mud-rock flow deceleration device in debris flow drainage groove |
| CN207176637U (en) * | 2017-08-24 | 2018-04-03 | 河南省煤田地质局三队 | A kind of blocking dam for mud-rock flow |
| CN209307959U (en) * | 2018-09-14 | 2019-08-27 | 四川省交通勘察设计研究院有限公司 | Terrace with edge stake and shuttle table type stake woods dam |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2001207431A (en) * | 2000-01-21 | 2001-08-03 | Shigeru Ito | Debris flow disaster protection dam |
| CN104878769A (en) * | 2015-06-19 | 2015-09-02 | 中国电建集团成都勘测设计研究院有限公司 | Debris flow protecting system |
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